The present invention concerns rotary dobbies and, more particularly, a mechanism to control the oscillations of the connecting rods operating the heald frames in such dobbies.
There are already known to be mechanisms of this type wherein, for each frame or connecting rod, said rod is mounted on a drive shaft by way of an eccentric interposed between said shaft and the connecting rod small end, and wherein said eccentric can be controlled for rotation, alternatively with the connecting rod or with the shaft, by means of a radial key, thanks to mechanical means adopted to shift said key to the outer position of engagement of the connecting rod small end, and to spring means adapted to return said key to the inner position of engagement of the shaft. There are also known to be mechanisms of the aforementioned type, wherein electromagnetic means are used to hold said key in the outer position of engagement of the connecting rod small end.
Nevertheless, none of these known mechanisms are fully satisfactory--especially at the increasingly higher speeds adopted on modern weaving looms--due to the masses and dimensions (and consequent inertias) of the mechanical elements forming such mechanisms, and to the power consumptions, heating and high noise levels which they involve.
The present invention provides a mechanism to control the oscillations of the connecting rods operating the heald frames in rotary dobbies, which has none of the above drawbacks and which is operates in the most reliable and efficient manner, even at the highest working speeds of the dobby and of the loom equipped therewith, while having at the same time a simple and convenient structure.